U.S. patent application number 10/924161 was filed with the patent office on 2006-02-23 for downhole oil and water separator and method.
Invention is credited to Syed Hamid, Roger Lynn Schultz, Harry D. JR. Smith, Adam Davis Wright.
Application Number | 20060037746 10/924161 |
Document ID | / |
Family ID | 35908572 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060037746 |
Kind Code |
A1 |
Wright; Adam Davis ; et
al. |
February 23, 2006 |
Downhole oil and water separator and method
Abstract
A downhole oil and water separator for an oil well includes a
water-selective membrane disposed in a production flowpath of the
well. The water-selective membrane is operable to selectively pass
water from the production flowpath to a disposal zone to increase
the concentration of oil in the production flowpath at the
surface.
Inventors: |
Wright; Adam Davis; (Dallas,
TX) ; Schultz; Roger Lynn; (Aubrey, TX) ;
Hamid; Syed; (Dallas, TX) ; Smith; Harry D. JR.;
(Montgomery, TX) |
Correspondence
Address: |
FISH & RICHARDSON P.C.
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Family ID: |
35908572 |
Appl. No.: |
10/924161 |
Filed: |
August 23, 2004 |
Current U.S.
Class: |
166/265 ;
166/228 |
Current CPC
Class: |
E21B 43/385
20130101 |
Class at
Publication: |
166/265 ;
166/228 |
International
Class: |
E21B 43/00 20060101
E21B043/00; E21B 43/34 20060101 E21B043/34 |
Claims
1. A well, comprising: a filter element disposed in a production
flowpath of a well at a level of a disposal zone; and the filter
element operable to pass from the production flowpath water
preferably over oil into the disposal zone.
2. The well of claim 1, further comprising the filter element
operable to increase a concentration of oil in the production
flowpath above the disposal zone.
3. The well of claim 1, the filter element comprising a
water-selective membrane.
4. The well of claim 3, the filter element comprising a plurality
of concentric perforated collector tubes with the water-selective
membrane covering the perforations.
5. The well of claim 3, the filter element comprising a plurality
of perforated collector tubes with the water-selective membrane
covering the perforations.
6. The well of claim 3, the filter element comprising a plurality
of overlapping perforated collector tubes with the water-selective
membrane covering the perforations.
7. The well of claim 1, further comprising one or more chokes
operable to maintain a differential pressure between the production
flowpath and the disposal zone.
8. The well of claim 1, wherein water separated from the oil is
communited to the disposal zone without mechanical pumping of the
water.
9. The well of claim 1, wherein fluid in the production flow path
is pumped at a velocity calculated to clean oil and solids off of
the filter element.
10. A well, comprising: a filter element disposed in a production
flowpath of a well; a filter element operable to pass from the
production flowpath water preferably over oil into the disposal
zone without mechanical pumping of the water.
11. The system of claim 10, the filter element comprising a
plurality of perforated collector tubes with a water-selective
membrane covering the perforations.
12. The system of claim 11, further comprising one or more chokes
operable to maintain a differential pressure between the production
flowpath and the disposal zone.
13. A downhole oil and water separator, comprising: a plurality of
perforated collector tubes each disposed laterally in a production
flowpath; a water-selective membrane covering perforation of the
collector tubes; the water-selective membrane operable to
selectively pass water from the production flowpath to a disposal
zone; and whereby the concentration of oil in the production
flowpath is increased.
14. The separator of claim 13, further comprising the perforated
collector tubes forming a serpentine flowpath.
15. The separator of claim 13, wherein the water-selective membrane
covers an exterior of the perforated collector tubes.
16. A well, comprising: a production zone producing oil and water;
a disposal zone; a production flowpath extending from the
production zone to the disposal zone and to a well surface; a
downhole oil and water separator system disposed in the production
flowpath, the separator system including a first stage separator
and a second stage separator operable to separate oil and water in
the production flowpath; and at least one of the first and second
stage separators comprising a water-selective membrane operable to
selectively pass water in the production flowpath to the disposal
zone.
17. The well of claim 16, wherein the first stage separator is an
oil and water gravity separator, the oil and water gravity
separator operable to separate formation fluids in the production
flowpath into an oil stream comprising a higher concentration of
oil than the formation fluid and a water stream comprising a higher
concentration of water than the formation fluid.
18. The well of claim 16, wherein the first stage separator is an
oil and water hydrocyclone separator, the oil and water
hydrocyclone separator operable to separate formation fluids in the
production flowpath into an oil stream comprising a higher
concentration of oil than the formation fluid and a water stream
comprising a higher concentration of water than the formation
fluid.
19. The well of claim 16, wherein the first stage separator is an
oil and water orbital separator, the oil and water orbital
separator operable to separate formation fluids in the production
flowpath into an oil stream comprising a higher concentration of
oil than the formation fluid and a water stream comprising a higher
concentration of water than the formation fluid.
20. The well of claim 17, the second stage separator comprising a
plurality of perforated collector tubes with the water-selectable
membrane covering the perforations, the second stage separator
operable to receive the water stream and to convey water passing
through the water-selective membrane to the disposal zone.
21. The well of claim 20, wherein the collector tubes are
concentric.
22. The well of claim 20, wherein the collector tubes are disposed
laterally in the production flowpath.
23. The system of claim 20, further comprising a downhole pump
operable to pump the water stream between the first and second
stage separators.
24. A method for separating of oil and water downhole in a well,
comprising: providing downhole in a well an oil and water separator
system including a water-selective membrane; filtering with the oil
and water separator system and without mechanical pumping formation
fluid in a production flowpath into an oil stream comprising a
higher concentration of oil than the formation fluid and a water
stream comprising a higher concentration of water than the
formation fluid; and producing the oil stream to the surface.
25. The method of claim 24, further comprising injecting the water
stream into a disposal zone in the well.
26. The method of claim 25, further comprising maintaining a
pressure differential between the production flowpath and the
disposal zone.
Description
TECHNICAL FIELD
[0001] Oil well production, and more particularly to a downhole oil
and water separator and method.
BACKGROUND
[0002] In oil well production operations, relatively large
quantities of water are frequently produced along with the oil. In
some oil wells, water and other by-products can amount to as much
as eighty to ninety percent of the total production yield. This is
particularly true during the later stages of production.
[0003] Various methods have been employed for separating the oil
from the water. For example, oil and water are typically pumped or
otherwise flowed together to the surface where they are treated to
separate the oil from the water. The water, after having been
pumped to the well surface and separated, is disposed of by removal
from the site or by pumping back into the well for injection into a
disposal layer.
[0004] Downhole separation has also been used to separate the oil
and water produced by a well. For example, hydroclones, dynamic
mechanical systems that use centralized forces to separate fluids,
and combinations of mechanical pumps and gravity separation have
been used for achieving separation of production fluids into water
and oil components. Hydrophilic and other semi-permeable membranes
have been used in connection with submersible pumps for downhole
separation.
SUMMARY
[0005] Oil and water are separated downhole using a water-selective
membrane. The separated water may be disposed of downhole and the
oil produced to the surface.
[0006] In a particular embodiment, the downhole oil and water
separator includes a plurality of perforated collector tubes
disposed laterally in the production flow path. In this embodiment,
the collector tubes may overlap or criss-cross to form a serpentine
or other high contact area flowpath. In another embodiment, the
water-selective membrane may be included in a filter element
disposed in the production flowpath at the level of the disposal
zone. In these and/or other embodiments, the production flowpath
may be filtered without downhole mechanical pumping.
[0007] Technical advantages of one or more embodiments of the
downhole oil and water separator and method include providing an
improved method and system for separating oil and water downhole
within a wellbore. For example, water may be separated from the oil
in the production flowpath and injected into a disposal zone
without use of mechanical pumping. In particular, water may be
removed from the production flowpath through the water-selective
membrane at the level of or otherwise in communication with a
disposal zone. Accordingly, equipment and production costs are
reduced.
[0008] Another technical advantage of one or more embodiments of
the downhole oil and water separator includes providing a
water-selective filter with increased efficacy. In particular, the
separator may include a plurality of perforated collector tubes
disposed laterally in the production flowpath or otherwise to form
a serpentine flowpath or otherwise increase surface contact area of
the filter for increased water removal. Accordingly, the
concentration of water in the produced fluids at the surface is
reduced.
[0009] These technical advantages may be present in none, some or
all embodiments of the downhole oil and water separator and method.
In addition, other technical advantages will be readily apparent
based on the following figures, description and claims.
DESCRIPTION OF DRAWINGS
[0010] FIG. 1 illustrates one embodiment of an oil well with a
downhole oil and water separator;
[0011] FIGS. 2A-2B illustrate additional embodiments of the oil and
water separator of FIG 1;
[0012] FIG. 3 illustrates another embodiment of an oil well with a
downhole oil and water separator;
[0013] FIGS. 4A-4B illustrate details of the oil and water
separator of FIG. 3; and
[0014] FIG. 5 illustrates still another embodiment of an oil well
with a downhole oil and water separator.
[0015] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0016] FIG. 1 illustrates one embodiment of a producing oil well
10. As used herein, oil well 10 includes any well producing or
operable to produce hydrocarbons from one or more subsurface
formations. The oil well 10 includes a wellbore 20 extending from
the surface 22 to a production zone 24. The production zone 24
produces oil and associated by-products including water. A disposal
zone 26 for water and/or other by-products may be disposed between
the surface 22 and the production zone 24. In another embodiment,
the disposal zone 26 may be disposed below production zone 24. In
yet another embodiment, the disposal zone 26 may comprise a portion
of the production zone 24. Thus, the production and disposal zones
24 and 26 may be disparate formations separated by intermediate
formations or may comprise disparate areas of a common
formation.
[0017] Wellbore 20 is cased with casing 30 which may be cemented in
place at the bottom of wellbore 20. Perforations 32 may be formed
in the casing 30 at the level of production zone 24. Similarly,
perforations 34 may be formed in the casing 30 at the level of the
disposal zone 26. The perforations 32 in the production zone 24
allow formation fluids 36 including oil and water to enter into the
interior of the casing 30 for treatment and production.
Perforations 34 in the disposal zone permit water 38 separated from
the formation fluid 36 to be discharged, disposed of or otherwise
injected into disposal zone 26. The perforations 32 and 34 may be
formed by conventional or other suitable techniques. In another
embodiment, the production tubing may have an open bottom in place
of or in addition to perforations.
[0018] A production tubing 40 extends in the wellbore 20 from a
surface wellhead 42 to the production zone 24. An annulus 46 formed
between the casing 30 and the production tubing 40 is sealed off by
packers 44 at or near the upper and lower boundaries of the
disposal zone 26. The packers 44 may be conventional production or
other suitable packers positioned to isolate in the annulus 46 at
production zone 24 from the annulus 46 at the disposal zone 26. The
production tubing 40 includes perforations 48 to allow formation
fluids 36 to enter into the interior of the tubing 40. The
production tubing 40 defines, in the illustrated embodiment, a
production flowpath 50 from the production zone 24 to the wellhead
42. Formation fluids 36 may otherwise enter into the production
tubing 40.
[0019] The production tubing 40 includes a downhole oil and water
separator 52 at, in one embodiment, the level of the disposal zone
26. The oil and water separator 52 may be otherwise suitably
positioned in the flowpath 50. For example, the oil and water
separator 52 may be disposed adjacent to the production zone 24.
The downhole oil and water separator 52 is operable to separate at
least some water 38 from oil in the production flowpath 50. The
separated water 38 may include a minority oil phase. Thus, the
downhole oil and water separator 52 may partially separate,
substantially separate or completely separate the oil and water in
the production flowpath 50. As used herein, water 38 may include
water as well as associated by-products in the formation fluid 50.
Oil may be any suitable hydrocarbon or other petroleum product.
[0020] The downhole oil and water separator 52 includes a filter
element 54. In one embodiment, the filter element 54 may have a
height substantially equal to the height of the disposal zone 26.
In other embodiments, the filter element 54 may have a height
greater than, substantially greater than, less than, or
substantially less than that of the disposal zone 26. The filter
element 54 may be cylindrically shaped and in direct fluid
communication with the disposal zone 26 via annulus 46.
[0021] The filter element 54 comprises a water-selective membrane.
The water-selective membrane may be a hydrophilic membrane or other
material that has a strong affinity for water. Such materials may
be sized to pass smaller water molecules while blocking larger
hydrocarbons. Other materials may include expanded
polytetra-fluoro-ethylene (EPTFE) and non-expanded PTFE.
[0022] One or more chokes 60 may be provided in the production
tubing 40 to control differential pressure in the production tubing
40 between the levels of the production zone 24 and the disposal
zone 26 and/or between the production tubing 40 and the disposal
zone 26. Thus, for example, formation fluids 36 in the production
tubing 40 at the level of the disposal zone 26 may have a pressure
that is 3 to 5 pounds per square inch (psi) higher than that of the
disposal zone 26 to ensure the flow of water 38 is into the
disposal zone 26. The differential pressure may be suitably varied.
In some embodiments, the chokes 60 may be omitted. The choke may be
any suitable pressure regulation or control system.
[0023] In operation, formation fluids 36 including oil and water
enter into the production flowpath 50 via perforations 32 and 48 in
the casing 30 and production tubing 40, respectively. As previously
discussed, formation fluids 36 may enter the production flow path
50 via an open bottom or otherwise. Formation fluids 36 flow up the
production tubing 40 to the wellhead 42 based on reservoir
pressure. In a particular embodiment, a submersible or other pump
may be used for lift. As the production fluids 36 are conveyed
through the downhole oil and water separator 52, water 38 is
removed via the water-selective membrane of the filter element 54
to form separate water and oil streams. The water stream may have a
minority oil phase and/or be substantially or completely water.
Similarly, the oil stream may have a minority water phase and/or be
substantially or completely oil. The water stream 38 is conveyed
through perforations 34 in the production casing 30 or other
suitable openings to the disposal zone 26. Accordingly, the
concentration of oil in the formation fluids 36 reaching the
wellhead 42 is higher than that originally received from the
production zone 24.
[0024] FIGS. 2A-B illustrate additional embodiments of the oil and
water separator 52. In these embodiments, the filter element 52
comprises a plurality of perforated collector tubes with the
water-selective membrane covering the perforations. The collector
tubes may be any suitable piping or channel operable to convey
water 38 to the disposal zone 26. Water 38 is conveyed to the
disposal zone 26 when it carried to or toward the zone 26. The
perforations may be any openings suitable to receive water 38 from
the production flowpath 50. The membrane may be disposed outwardly
or inwardly of the collector tubes, or otherwise to selectively
pass water 38 from the formation fluid 36 into and/or along the
collector tubes. In particular, FIG. 2A illustrates a concentric
arrangement of collector tubes. FIG. 2B illustrates a lateral
arrangement of collector tubes.
[0025] Referring to FIG. 2A, the downhole oil and water separator
52 in this embodiment includes a concentric arrangement of
perforated collector tubes 80 in the filter element 54. Each
collector tube 80 is concentric to the others and, in the
illustrated embodiment, covered with the water-selective membrane
81. As described above, the water-selective membrane 81 may be
disposed outwardly or inwardly of each collector tube 80. Each
collector tube 80 communicates collected water 38 to the disposal
zone 26 through one or more tubes 82 extending from the collector
tube 80 to the perforation of the production tubing 40.
[0026] The collector tubes 80 form a series of concentric annular
flowpaths 84 through the downhole oil and water separator 52. The
annular flowpaths 84 provide an increased surface contact area
between the formation fluids 36 flowing in the production flowpaths
50 and the water-selective membrane 81 of the filter element 54.
Accordingly, a greater amount of water 38 may be removed from the
production flowpath 50 to minimize water produced at the surface
that must be reinjected.
[0027] Referring to FIG. 2B, the downhole oil and water separator
52 in this embodiment includes the plurality of perforated
collector tubes 90 disposed laterally in the production tubing 40
to create a serpentine flowpath 50 at the level of the disposal
zone 26. In this embodiment, each collector tube 90 is covered with
the water-selective membrane 92. Water 38 collected by the
collector tube 90 is conveyed into the annulus 46 between packers
44 and through perforations 34 to the disposal zone 26.
[0028] The serpentine flowpath 50 increases the surface area of the
filter element 54 exposed to the production flowpath 50 and
enhances water separation from formation fluids 36 produced to the
wellhead 42. In this embodiment, the filter element 54 may have
tens, hundreds or more collector tubes 90 each extending two-thirds
or more of the way across the diameter of the production tubing 40
and spaced within a diameter of each other. In a particular
embodiment, the tube of this or other embodiments may be spaced
such that fluid disturbances created by vortex shedding interact
with neighboring tubes. Also, in this embodiment, the collection
tubes 90 may have a width extending from one side to the other side
of the production tubing 40. In other embodiments, a plurality of
round, oval or other suitable collector tubes 90 may be disposed at
each level. Collector tubes 90 may be otherwise suitably configured
and/or disposed in the production flowpath 50 for separating water
38 from formation fluids 36.
[0029] FIG. 3 illustrates another embodiment of an oil well 100
with a downhole oil and water separator. In this embodiment, the
downhole oil and water separator is removable for easy replacement
when the water-selection membrane is clogged. The oil and water
separator 52 and/or filter element 54 of FIGS. 1 and 2A-B may be
similarly removable.
[0030] Referring to FIG. 3, and as described in connection with oil
well 10, oil well 100 may have a wellbore 120 extending from a
surface 122 to a production zone 124. A disposal zone 126 may be
disposed between the surface 122 and the production zone 124. A
casing 130 may include perforations 132 at the production zone 124
and 134 at the disposal zone 126. Production tubing 140 may extend
from a wellhead 142 to the production zone 124 and define a
production flowpath 150. Packers 144 may seal an annulus 146
between the casing 130 and the production tubing 140 at the upper
and lower boundaries of the disposal zone 126.
[0031] The downhole oil and water separator 152 is retrievably
disposed in the production tubing 140. In one embodiment, the
production tubing 140 includes a landing nipple with a lock mandrel
connector 156 to allow the downhole oil and water separator 152 to
be periodically removed and replaced. In this embodiment, a set of
seals 158 may be disposed between the filter element 154 and the
production casing 140. A choke 160 may be disposed at the top of
the oil and water separator 152 to maintain a differential pressure
between formation fluids 136 in the filter element 154 and the
water or other fluid in the disposal zone 126.
[0032] The filter element 154 comprises a filter stack including
criss-crossing collector tubes 162. The collector tubes 162 may
each be perforated and extended laterally across the filter element
154. The collector tubes 162 may be covered internally, externally
or otherwise with the water-selective membrane to filter out water
138 from formation fluids 136 flowing through the filter element
154.
[0033] In operation, formation fluids 136 flow at pressure from the
production zone 124 through perforations 132 and into the
production tubing 140. As the formation fluids 136 travel through
the filter element 154, water 138 is separated out through the
water-selective membrane and communicated by the collector tubes
162 through perforations 164 in the production tubing 140 and
perforations 134 in the casing 130 to disposal zone 126. At the
outlet of the filter element 154, the formation fluids 136 include
a higher concentration of oil than the fluids received from the
production zone 124. In a particular embodiment, all, substantially
all, or the majority of the water 138 may be removed from the
formation fluids 136 by action of the downhole oil and water
separator 152. In another embodiment, a majority, but a reduced
amount of the formation fluids 136 may comprise water after
filtering.
[0034] Although not illustrated in FIG. 3, a downhole pump may be
used at the level of the production zone 124 or elsewhere to
increase pressure in the production flowpath 150 in the production
tubing 140. The pump may be a submersible pump or a progressive
cavity pump. For example, for a submersible pump, a power cable may
be run to the pump through the packer in the permanent annulus
146.
[0035] A pump may be used to control the flow rate of fluid in the
downhole oil and water separator to continually clean the membrane.
For example, at flow rate of 10-30 feet per second, oil and solids
that otherwise accumulate may be scraped off, eroded or otherwise
removed from the membrane to leave it exposed. In another
embodiment, a pump may be used to inject separated water 138 into
the disposal zone 126. For example, in an embodiment in which the
disposal zone 126 is located below the level of the producing zone
124, the downhole oil and water separator 152 may be positioned at
the level of the production zone 124 and separated water 138 may
flow by gravity downward to a pump coupled to an end of the oil and
water separator 152. The pump may force or otherwise inject the
water 138 into the disposal zone 126. As previously described, a
mechanical pump may be completely omitted and flow otherwise
controlled.
[0036] FIGS. 4A-B illustrate details of one embodiment of the
filter stack of FIG. 3. In particular, FIG. 4A illustrates
criss-crossing collector tubes 162 of the filter element 142. FIG.
4B illustrates a cross section of the collector tubes 162 along
line 4B in FIG. 4A.
[0037] Referring to FIG. 4A, perforated collector tubes 162 extend
across the filter element 154 and criss-cross one another in the
flowpath 150 to increase the surface area of the filter element 152
for filtering water 138. The collector tubes 162 may be round, oval
or may have an enlarged cross section perpendicular to the
production flowpath 150 to maximize fluid flow over the tubes 162.
Filtered water 138 exits each end of the collector tubes 162 into
the inner annulus 159 between the filter element 154 and the
production tubing 140 and passes through perforations 164 in the
production tubing 140 and similar perforations 134 in the casing
into disposal zone 126. The collector tubes 162 may be otherwise
suitably disposed in the production flowpath 150. In addition,
several collector tubes 162 may be disposed in the filter element
154 at each level.
[0038] Referring to FIG. 4B, the perforated collector tubes 162 may
each be covered inwardly, outwardly or otherwise with the
water-selective membrane 166. In the illustrated embodiment, the
water-selective membrane 166 covers an outer periphery of the
collector tube 162. The water-selective membrane 166 passes water
from the formation fluids 136 through perforations 168 into an
interior of the collector tube 162. A wire mesh or other suitable
perforated material 170 with openings 172 may overlap and protect
the water-selective membrane 166. The protective material 172 may
be in some embodiments omitted. As previously described, the
water-selective material may be any material suitable to
selectively pass water over oil in a production environment.
[0039] FIG. 5 illustrates another embodiment of an oil well 200
with a downhole oil and water separator. In this embodiment, as
described in more detail below, the oil and water separator
includes a first stage separator and a second stage separator. The
oil and water separator 52 of FIG. 1 and/or 152 of FIG. 3 may
likewise include a multi-stage separator. In addition, the downhole
oil and water separator may have more than two stages, with a
water-selective membrane as the final stage.
[0040] Referring to FIG. 5, and as described in connection with oil
well 10 and oil well 100, oil well 200 may have a wellbore 220
extending from a surface 222 to a production zone 224. A disposal
zone 226 may be disposed between the surface 222 and the production
zone 224. A casing 230 may include perforations 232 at the
production zone 224 and perforations 234 at the disposal zone 226.
Production tubing 240 may extend from the wellhead 242 to the
production zone 224 and/or downhole oil and water separator 252 and
define a production flowpath 250. Packers 244 may seal an annulus
246 between the casing 230 and the production tubing 240 at the
upper and lower boundaries of the disposal zone 226.
[0041] The downhole oil and water separator 252 may be a
multi-stage separator and may in one embodiment include a first
stage separator 256 and a second stage separator 258. Additional
stages may also be included. The first stage separator 256 may be a
gravity oil and water separator at a level of the production zone
224. The first stage gravity oil and water separator may be used,
for example, in wells with low overall flow rates. In other
embodiments, a hydrocyclone or orbital separator may be used at the
level of the production zone 224 or elsewhere. The gravity oil and
water separator 256 may have an inlet 260, an oil outlet 262 and a
water outlet 264. The oil outlet 262 of the gravity oil and water
separator 256 may be connected to the production tubing 240 for
production of the egress oil stream to the wellhead 242. A pump 270
may be disposed at the oil outlet 262 of the gravity separator 256
to assist in production of the oil stream to the surface 222.
[0042] The water outlet 264 from the gravity oil and water
separator 256 may feed into the second stage separator 258. In this
embodiment, the second stage separator 258 includes a filter
element 272 with a water-selective membrane. A pump 274 may be
disposed at the water outlet 264 to pressurize water flowing into
the second stage separator 258.
[0043] In the second stage separator 258, water 238 passing through
the water-selective membrane is injected into the disposal zone
226. Oil and/or water not passing through the water-selective
membrane may be recirculated through a recirculation passage 276
back to the first stage separator 256. In this embodiment, the
water-selective membrane in the second stage separator 258 may be
used to clean-up water output from the first stage separator 256.
The first stage and/or second stage separators 256 and 258 may be
configured in any suitable manner. For example, the disposal zone
226 could, as previously described, be below the level of the
production zone 224. In any event, the water-side outlet of the
first stage separator 256 is circulated past the water-selective
membrane, which allows water to pass, and re-circulates the
remaining oil-enriched water through the first stage separator 256.
The use of the first and second stage separators 256 and 258 may
reduce the amount of water produced to the surface 222 from the
single-stage separator embodiment.
[0044] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. For example, a sump may be formed beneath a
production zone such that solid debris falling out from the
filtering process will not build up and interfere with production.
Accordingly, other embodiments are within the scope of the
following claims.
* * * * *